A French man was charged in Greece on Sunday over a boat accident that left two dead and another person seriously injured, state TV ERT reported.
The 44-year-old was charged with negligent manslaughter by a prosecutor and given 24 hours to prepare his defence, ERT said.
The man's lawyer Nikos Emmanouilidis had earlier told reporters that his client "will assist in every way any request by the Greek authorities."
The suspect has admitted to driving a 10-metre (32-foot) speedboat which struck a smaller wooden fishing boat on Friday evening near the Peloponnese resort of Porto Heli, 170 kilometres (105 miles) southwest of Athens.
The collision killed two elderly Greek men on board. A 60-year-old Greek woman, reportedly their sister, was seriously injured and taken to Athens for treatment.
The suspect could not be located for several hours after the incident before turning himself in on Saturday.
He has denied trying to evade arrest, and claims he was also injured in the incident and had sought first aid.
The suspect has said he did not see the fishing boat, which may have had insufficient lighting, state news agency ANA reported.
He has taken a blood alcohol test, with the results to be available on Monday.
"The first indications point to excessive speed by the powerboat driver," Merchant Marine Minister Yiannis Plakiotakis told ERT on Saturday.
Ten other French nationals who were also on the speedboat -- two men, three women and five children aged three to 14 -- were initially taken to Porto Heli for questioning after helping to bring the injured woman and one of the bodies to shore, the coastguard said.
They were all released on Saturday.
Speedboat accidents involving swimmers or other boats are common in Greece during the busy summer holiday season.
Another speedboat on Friday injured a 32-year-old swimmer at the Athens coastal suburb of Glyfada. The driver was arrested.
In 2016, four people including a four-year-old girl were killed when a speedboat sliced into their wooden tourist vessel near the island of Aegina.
Nobody was sanctioned as the prime suspect, an elderly Greek man, died a year after the accident.